Regulating roentgen-ray tubes



(No Model.)

B. THOMSON. REGULATING ROENTGEN RAY TUBES.-

No. 591,899. Patented Oct. 19, 1897'.

\AATHEEIEEEI v M UNITED STATES PATENT CFEICE.

ELlllU THOMSON, O-F SWAMPSCOTT, MASSACHUSETTS, ASSIGN OR TC THE GENERALELECTRIC COMPANY, OF NEW YORK.

REGULATlNG ROENTGEN-RAY TUBES.

SPECIFICATION forming part of Letters Patent No. 591,899, dated October19, 1897.

Application filed August 1, 1897. Serial No. 647,035. (No model.)

T 0 all whom it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, county of Essex, Commonwealth ofMassachusetts,have invented certain new and useful Improvements inRegulating Roentgen-RayTubes, (Case No. 599,) of whichthe following is aspecification.

My invention relates to the vacuum in Roentgen-ray tubes, and has forits object the provision of means for regulating the vacuumautomatically if need be, and also it provides that the regulatingapparatus shall be in a sense independent of the main raytube, so thatthe regulating apparatus may be applied to various tubes. This isimportant in case an accident happens to the raytube itself withoutinjury to the regulating apparatus, or in case an accident happens tothe regulating part of the structure which does not involve theray-tube. Hitherto the regulating arrangement of the Roentgen-ray tubehas been combined in one structure with the tube, which involves theloss of the whole structure-tl1at is, the ray-tube itself and theregulating apparatus-when either are damaged, as by electrical punctureor by accidental breakage. In my invention the automatic regulation isaccomplished by means of the production of heat in a vaporizablematerial, the heating being effected by current passing in theregulating-tube or regulating attachment. The regulating attachment, inmy invention, may be applied to existing forms of Roentgen-ray tubes,and may be made and sold as a separate device for use with existingforms of regulating-tubes, such as those containing a side tube having avaporizable substance from which vapor can be driven off by slightheating in order to counteract the gradual increase of vacuum whichtakes place in working Roentgen-ray tubes. I apply my arrangement orregulating attachment to the tube generally in a shunted circuit fromthe main terminals, so that if the resistance to the passage of adischarge increases between the main terminals supplying theRoentgen-ray tube there is a diversion or shunting to the side branchcontaining the spark-gap and regulating attachment. By making theregulating attachment separate from the Roentgen-ray tube I am enabledto standardize both, so that any one of my regulating attachments may beused upon any one of the Roentgen-ray tubes, and the risk of breakagewhich would existwhen both are combined into one structure, as also theloss due to the breakage, would be greatly diminished.

To these ends I have devised my present invention, which consists of anouter separate tube or exhausted bulb, so shaped that it may be applieddirectly to the small tube or extension containing the volatilizablecompound. This bulb is contained in a shunt around the ray-tube andcontains a cathodeterminal of the usual concave disk form, preferably,and a suitable anode-terminal placed at any convenient place within thebulb. I prefer to so shape the bulb that it will readily maintain itselfin position.

The drawings annexed show an embodiment of my invention, Figure 1showing the tube and auxiliary bulb referred to, with their connections,and Fig. 2 showing an end View of the bulb alone.

A is the Crookes tube, of now well-known form; B B, the terminals of theexciting apparatus, such as an induction-coil.

C C are the terminals of the shunt or regulating spark-gap.

The tube A is provided'with the tubular extension a, in which is thevolatilizable compound, such as potassium hydrate. I

A is the auxiliary bulb or. tube, of such shape as may be preferred.That shown is a desirable one. It is provided with an exterior cap ordepression a, within which may be seated the tubular extension on of theCrookes tube, and with which it is designed to register. To facilitatethe transmission of heat to the material in the extension a, a littleoil may be placed, if desired, in the cup. The bulb A has the cup orcathode-terminal opposite the cup, the discharge passing from suchterminal to the anode-terminal within the same tube. Each terminal isconnected, respectively, to the terminals of the main tube A, as shown.It is to be understood that the spark-gap C C, which is the regulatingspark gap, is shorter than the spark-gap between B B, or the terminalsof the exciting apparatus,

and of such length as to only allow a spark to pass when the oppositionto the discharge in the main tube has risen to that point which causesit to cease to be effective for the particular kind of Roentgen rays tobe obtained from it. Also, the spark-gap C C"may evidently be put in anypart of the circuit or con nection leading from the cathode to the anodeterminal through the regulating-bulb A.

The operation is as follows: Supposing the tube A to be in workingcondition and the spark-gap C C adjusted, as indicated, with the partsin place, as shown in the figures, then if the vacuum in the tube A, dueto the continued use of the tube, rises, as it generally does, it mayreach that point which will force the discharge to pass over thesparkgap C Cthat is, it will so fail to shunt the terminals of theexciting apparatus as to cause an increased potential to be exhibitedbetween those terminals. The side circuit including the spark-gap C Cincludes also the regulating-bulb A, and the bombardment from itscathode-rays hits the cup in contact with which, or close to which, isplaced the regulating-tube A, containing the volatile compound. The heatso developed volatilizes a portion of the compound, or decomposes aportion thereof, giving out gas whiehlowers the vacuum in the main bulbA, and restores its condition of working. Of course it is understoodthat the exciting apparatus whose terminals are at B B is not to be suchas would maintain a constant potential between the terminals, but is tobe similar to a Ruhmkorfi induction-coil in its nature. It is also to beunderstood that the spark-gap C C might be replaced by an extremely-highresistancesuch as. a small glass tube filled with water or other fluid,the leakage through which would be determined by the resistance. It willalso be understood that where the discharges are of high frequency, andalternating with Crookes tubes having an extension containing avolatilizable substance or com-' pound, a separable vacuum-adjusterconsisting of an exhausted auxiliary bulb having a. portion fitted tothe main tube for the transfer of heat thereto, and containing terminalsfor the passage of electric discharges.

2. The combination with a Crookes tube to be maintained at a criticalvacuum for the production of Roentgen rays, of an extension from themain tube containing a salt or substance volatilizable by heat, andaseparate exhausted bulb registering with the extension and includedin ashunt around the main tube.

3. The combination with a Crookes tube having an extension containing avolatilizable salt or compound, of an auxiliary bulb fitted to orregistering with said extension and provided with terminals, whereby itmay be included in a shunt around the main tube, with a regulatingspark-gap or high resistance in the shunt-circuit.

4. As a new article of manufacture, an exhausted bulb having adepression or recessed portion adjusted or placed within the range ofbombardment of cathode-rays within the 'said bulb by the passage ofelectric discharges through the same, for the purpose specified.

Lynn, Massachusetts, August 2, 1897.

ELIHU THOMSON. Witnesses:

JOHN W. GIBBONEY, HENRY O. XVESTEND RP.

